In specific instances it is necessary for a physician to obtain a sample of bone marrow. Most commonly, the sample is biopsied to determine the presence of disease, although other purposes may exist, e.g., recovery of cells for transplantation. A biopsy may be prescribed to remove liquid aspirates from the marrow space as well as a core sample of the bone marrow to determine whether cancer or other disease is present. Liquid aspirate must be drawn from the marrow cavity for cytological study and a core sample of marrow material must be obtained if histological study is desired.
In the conventional prior art procedure, the physician penetrates the hard bone of the patient with a cannula/trocar combined needle from a bone marrow biopsy set (see, e.g., U.S. Pat. No. 3,628,524, inter alia, to Jamshidi, and U.S. Pat. No. 7,278,972 to Lamoureux, et al.). The needle is twisted down through the cortex of the bone into the marrow space. Once the marrow cavity is accessed, the trocar is removed and a syringe is attached to the opening where the trocar resides. A liquid sample can be withdrawn from the marrow space using the syringe attached to the needle. Alternatively, a core sample of marrow can be obtained. The hollow center of the cannula needle is specially shaped with a first proximal diameter, tapering to a distal end of a second diameter. The needle is tapered in the last 2 to 3 centimeters of the distal end to a smaller sharpened opening with a cutting edge. This reduced second diameter of the large bore needle assists in capturing and holding a core sample instead of a liquid sample.
To obtain a core sample using this Jamshidi (R) method, the bone cortex is penetrated in the same manner as for a liquid sample, but once the trocar is removed, the hollow cannula is driven farther manually, into the marrow space, to obtain a solid core of marrow. A core sample of a certain length is obtained by inserting a rod into the cannula, and driving the cannula into the marrow until the proximal end of the rod rises to the desired length above the proximal end of the cannula. To preserve the integrity of the core sample, the physician rocks the needle from side to side to break the distal end of the sample free from the rest of the matrix of marrow. The cannula is then removed from the patient and the marrow sample is removed by pushing the rod all the way through the cannula, discharging the sample into a sample bottle.
This apparatus and method are widely used because the apparatus is single-use disposable and reasonably priced. The main drawback of this apparatus and method is that it requires significant manual axial pressure and rotation to drive the needle through the bone cortex, all the while attempting to sense the interface between the cortex and the marrow and avoid either penetrating the marrow completely or mechanically damaging the marrow before a sample can be obtained. Even the most skilled practitioners often find it necessary to reinsert the instrument, causing another wound and taking more time.
The manual procedure has been improved more or less, cost notwithstanding, by automated devices. A number of prior art devices automate obtaining biopsies, but most of them are suitable for soft tissue use only. (See, e.g., U.S. Pat. No. 7,189,207 to Viola, comprising a trocar driver, a knife driver and firing module.) U.S. Pat. No. 4,919,146 to Rhinehart incorporates an electric drill and a syringe into a hand-held device, but the patent specification does not mention bone or marrow biopsy nor does the device appear to be suitable for those procedures. In any case, it appears that the drill bit of Rhinehart will not produce a core sample with sound architecture. One prior art device intended to solve the problem of manual control and get a good intra osseous sample in one operation is U.S. Pat. No. 6,022,324 to Skinner, comprising a sampling needle driven by a gun which applies axial bone-penetrating force of up to 200 pounds. This force is supplied by an electric motor or gas cylinder. It incorporates a syringe to withdraw a sample after actuation of the firing mechanism. A problem here is that, while it reduces the time required to get a sample, it would seem not to provide sufficient sample quality and reproducibility because of the wide patient-to-patient variation in soft tissue depth and thicknesses of bone cortex and marrow, and the likely trauma caused by the impact of the syringe on the tissues. A later patent, U.S. Pat. No. 6,626,848 to Neuenfeldt, moves the sampling needle in a reciprocal rotating motion about its axis as it is guided into the bone and thence into the marrow. The sampling is performed in a manner similar to the aforementioned Jamshidi method after the bone cortex is penetrated. The unsolved problem here is that no provision is made for withdrawal of both liquid and solid samples in one operation and the use of relatively-inexpensive tissue-contacting parts for disposal.
What is needed is a power-driven device that not only accomplishes the above-mentioned goals of improved sampling success and reduced time requirement, but also improves, rather than diminishes, the physician's tactile sense of cannula placement. It is also highly desirable to provide these qualities in a device that has single-use disposable tissue and liquid contact parts, the parts being of simple construction and reasonable price, operable by a mechanism that does not require large capital investment.